Remote Triggering in Continental China

Recent studies have shown that large earthquakes are capable of triggering microearthquakes and deep “non-volcanic” tremor at regional and teleseismic distances. These types of dynamic triggering are found not only at active plate-boundary faults, but also relatively stable intraplate regions. However, it is still not clear what are the necessary conditions and most plausible physical models for dynamic triggering. Here we perform a comprehensive analysis of dynamic triggering in Continental China associated with recent large earthquakes around the world. We first examine remotely triggered seismicity around the Babaoshan and Huangzhuang-Gaoliying faults near Beijing, China. The triggered earthquakes are identified as impulsive seismic arrivals with clear P- and S-waves in 5 Hz high-pass-filtered three-component velocity seismograms during the passage of large amplitude body and surface waves of large teleseismic events. We find that this region was repeatedly triggered by 4 earthquakes in East Asia, including the 2001 Mw7.8 Kunlun; 2003 Mw8.3 Tokachi-oki; 2004 Mw9.2 Sumatra; and 2008 Mw7.9 Wenchuan earthquakes. In most instances, the microearthquakes coincide with the first few cycles of the Love waves, and more are triggered during the large-amplitude Rayleigh waves. Such an instantaneous triggering by both the Love and Rayleigh waves is similar to recent observations of remotely triggered ‘non-volcanic’ tremor along major strike-slip faults and subduction zones, and can be explained by a simple Coulomb failure criterion. We are able to locate 5 of the earthquakes triggered by the Kunlun and Tokachi-oki earthquakes. These events occurred close to the Babaoshan and Huangzhuang-Gaoliying faults at shallow depth (< 5 km). We suggest that these events occur near the transition between the velocity strengthening and weakening zones in the top few kms of the crust, and are likely driven by relatively large dynamic stresses of few tens of KPa. Our next step is to examine the seismic data generated by recent large earthquakes and recorded by both permanent network and temporarily deployed seismic array in North China. Through these systematic studies, we hope to identify the necessary conditions and physical models for dynamic triggering in intraplate regions.